8.2.1 Vehicle Technology Improvements

Vehicle technology improvements normally involve proper maintenance, improving
the engine or vehicle body, or reducing inertia with the main aim of reducing
the energy intensity (energy use per useful product) and so reducing carbon
emissions. Regular servicing, including regular tire and oil checks, and engine
tuning can lead to fuel savings of 2-10% (Davidson, 1992; Pischinger and Hausberger,
1993). Use of three-way catalytic converters along with electronic fuel injecting
systems can result in reduction of ozone precursors (unburned HC, CO, NOx)
emitted from gasoline cars and heavy-duty vehicles, but the effect on global
warming is uncertain because the impact of fuel consumption is also uncertain
(IPCC, 1996). Improved combustion by use of gas turbines and low-heat-rejection
engines can potentially result in higher efficiency and, thus, in lower emissions,
but there will be a need for high temperature materials along with compatible
high temperature lubricating systems. Also, direct-ignition stratified-charge
engines can be more efficient because of their ignition enhancing qualities.
Details of these potential reductions are given in Table
8.2. The potential exists for increasing vehicle mileage and, therefore,
energy intensity by reducing the aerodynamic drag and rolling resistance leading
to improved efficiency and, thereby, reducing the emissions (ETSU, 1994; DeCicco
and Ross, 1993). Similarly, through size reduction, material substitution or
component redesign, the inertia can be reduced and so lower the fuel consumption
(DeCicco and Ross, 1993). Improving the transmission system to electronically
allow for optimal speed and load conditions can result in energy savings and
reduced emissions (Tanja et al., 1992; NRC, 1992). More details of these
potential reductions are summarised in Table 8.3.

Trends show that if priorities shift among manufacturers and users, improvements
of 10-25% in energy intensity may be achievable on cars by 2020 at a higher
cost, but the potential for commercial vehicles will be smaller. However, fuel
savings and environmental gains may be offset by the increase in number of vehicles
and driving (Wootton and Poulton, 1993).

The trend in buses for higher level of comfort and safety, and more powerful
engines has tended to increase fuel consumption per seat compared with old buses,
but this can be reduced by using advanced composite materials and turbo-compound
diesel engines. Electric buses are in use as minibuses in urban areas, but they
have higher GHG emissions than diesel buses when the primary emissions than
diesel buses when the primary energy used is from fossil sources. Hybrid buses
(diesel/electric) are now being tested because they can save up to 30% in energy
if the motor/generator efficiency is about 85%. Alternative fuels (CNG, alcohol
fuels and vegetable oils) are used in buses and when rapeseed methyl ester is
used as substitute for diesel, life-cycle GHG emissions can be reduced by 25-50%
(IEA/OECD, 1994). Use of turbo-charging and charge cooling in engines of trucks
improves the fuel economy and so reduces GHG emissions, but retarding fuel injection
worsens the fuel economy. Potential exists for improvement in fuel economy based
on developments of new engine materials (IEA/OECD, 1993). Fuel economy can also
be improved in the design of trains. About 5-10% savings is possible in diesel
locomotives and up to 30% if a regenerative braking system is used in urban
metro systems; 15% savings could be realised in suburban train systems and 5-10%
for inter-city systems.

Energy intensity in aircraft can be improved with engine modifications and
new engine designs. Future improved supersonic engines that are expected after
2010 may lead to an increase in energy efficiency and lower emissions, but this
improvement could lead to increase traffic movements (Balashov and Smith, 1992).

Energy intensity for boats can be improved by modifying marine engines by making
improvements in the hull and propeller designs that could yield to higher energy
gains. The use of vertical-axis turbines as sails can assist the engine and
result in energy savings (CEC, 1992).